Branching filter

Abstract

A branching filter includes an antenna terminal, a transmission signal terminal, a reception signal terminal, a transmission filter element, and a reception filter element. At least one of the transmission filter element and the reception filter element includes a longitudinally coupled resonator filter element having first and second IDT electrodes arranged along a direction of propagation of an elastic wave. The first IDT electrode includes a first end connected to the antenna terminal. The second IDT electrode includes a first end connected to one of the transmission signal terminal and the reception signal terminal. The longitudinally coupled resonator filter element further includes an inductor connected in series between a second end of the first IDT electrode and a ground potential.

1. A branching filter comprising:
 an antenna terminal; 
 a transmission signal terminal; 
 a reception signal terminal; 
 a transmission filter element disposed between the antenna terminal and the transmission signal terminal; and 
 a reception filter element disposed between the antenna terminal and the reception signal terminal; wherein 
 at least one of the transmission filter element and the reception filter element includes a longitudinally coupled resonator filter element including first and second IDT electrodes arranged along a direction of propagation of an elastic wave, the first IDT electrode having a first end connected to the antenna terminal, the second IDT electrode having a first end connected to one of the transmission signal terminal and the reception signal terminal; 
 the longitudinally coupled resonator filter element further includes an inductor connected in series between a second end of the first IDT electrode and a ground potential and arranged to provide an attenuation range in a region higher than a pass band of the at least one of the transmission filter element and the reception filter element; and 
 the reception filter element includes the longitudinally coupled resonator filter element, and the transmission filter element includes a ladder filter element. 
 
     
     
       2. The branching filter according to  claim 1 , wherein the inductor is connected to a first ground electrode, and the second IDT electrode includes a second end connected to a second ground electrode separated from the first ground electrode.